Art of refining



Hatented Feb. 20, 1940 UNETED STATES ART OF REFINING Edwin J. Earth, Chicago, 111., assignor to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Application May s, 1936,

Serial No. 77,925

2 Claims.

This invention relates to improvements in petroleum hydrocarbon oils. More particularly, it relates to inhibition of oxidation in petroleum oils, lubricating oils in particular, having a Saybolt Universal viscosity upwards of 50 seconds at F. by the addition thereto of an organic oxidation inhibitor. The invention includes a new organic oxidation inhibitor and an improved compounded petroleum oil containing the new oxidation inhibitor of the invention.

Petroleum oils have a tendency to form sludge and gummy and resinous substances. The formation of these substances is generally objectionable, particularly so where it is desired to maintain the oil in a continuously uniform condition. One generally accepted explanation assumes that the formation of these substances results from oxidation. Whatever may be the true explanation, it is known that when lubricating oils are used in internal combustion engines, for example, these undesirable substances form and, as formed, are commonly referred to as sludge.

Sludge may appear in a variety of forms ranging from deposits quite soft and gelatinous in nature to those of the texture of coke. The results arising from the presence of sludge deposits are varied, ranging from accumulations in oil pans and other relatively stagnant locations which appear objectionable but which actually do no harm, to deposits in such vulnerable spots as ring grooves, oil screens and filters, where actual interference with engine operation occurs. Sludge, in addition to being objectionable in the respects noted, causes an increase in viscosity accompanied by an increase in the variability of viscosity with changing temperature. Where the maintenance of continuously uniform properties is desirable, such changes are, of course, objectionable.

In accordance with the present invention, sludge formation and such changes with respect to viscosity are inhibited, thereby promoting uniformity of properties and increasing the useful life of the oil, the period over which those properties remain within limits appropriate to the particular use.

It is an object of the present invention to provide an oxidation inhibitor which when incorporated in petroleum oils 'in proper proportion will minimize or inhibit oxidation of the oil. A further object of the invention is to provide a compounded petroleum oil containing the new inhibitor of the invention which has greatly reduced tendencies to form sludge and similar oxidation products. A still further object is to provide an oxidation inhibitor which when incorporated in a petroleum oil, as defined herein, will inhibit oxidation and reduce the tendency oxidation inhibiting properties.

of the oil to undergo changes with respect to viscosity.

I have discovered that retene (methyl isopropyl phenanthrene) C18H18 exhibits excellent When added to petroleum oils, having a Saybolt Universal viscosity upwards of 50 seconds at 100 F., in amounts upward of about 0.05 percent by weight, oxidation with its resultant sludge formation is substantially inhibited, and changes with respect to viscosity are retarded. The addition .of retene in amounts approximating 0.1 percent by weight, for example, is generally advantageous.

It might be noted that extensive investigations have shown that substances known to be oxidationinhibitors in arts other than the petroleum art have little or no value as applied to petroleum oils. In a number of instances tests have shown that some of these known oxidation inhibitors were detrimental when incorporated in petroleum oil and actually caused an increase in the rate of sludge formation.

As the value of an oil which is to be used over and over again, or subjected to continuous use, for example, depends largely upon its stability, tests have been devised to determine the stability of an oil in particular respects. Thus tests have been developed which enable one to determine to what extent an oil will sludge when in use, and these tests furnish a means for evaluating the oil in this respect and to determine the efliciency of oxidation or sludge inhibitors. One of these tests is known as the Indiana Oxidation Test. This test is described ln an article entitled Causes and effects of sludge formation in motor oil appearing on pages 167, 168 and 181 of the Journal of the Society of Automotive Engineers for May, 1934, where the problem of sludge formation is treated at considerable length. This Indiana Oxidation Test, to which reference is made hereinafter, ofiers a meanse of determining the so-called sludging time of .an oil.

In this test 300 cc. of the oil to be tested are placed in a glass tube twenty inches long by one and three-quarter inch internal diameter, secured in an oil bath maintained at a temperature sumcient to keep the test oil at 341 F. The level of the oil in the tube should be well below the bath level. Air is passed through the oil, being introduced through a glass tube of three-sixteenth inch internal diameter at a point about one-quarter inch from the bottom of the glass tube at a rate of ten liters per hour. Periodically, depending on the oxidation characteristics of the oil, 25 cc. of oil are removed, 10 grams of which are immediately weighed into a tared Erlenmeyer flask. This portion is diluted with 100 cc. A. S. T. M. precipitation naphtha IOY and allowed to stand three hours before filtering through a Gooch' crucible. The crucible containing the insolubles is washed with ap'proximately 100 cc. of naphtha after which it is dried one-half hour at 300 F. and weighed. The amount of insoluble matter is expressed in milligrams per ten grams of oil. A suflicient number of samples should be taken for test to determine accurately the sludging time, that is, the time required to form ten milligrams of naphtha insolublematter-per ten grams of oil. When employing the above test it is common to also determine the 100 milligram point, i. e., the time to form 100 milligrams of insolubles, but it Will be understood that the sludging time is the time required to form 10 milligrams of naphtha insoluble material per 10 grams of oil.

The determination of viscosity increase, which becomes the more important criterion when the sludging time is much over 50 hours, is made by taking a 100 cc. sample every 50 hours. This sample is promptly run for viscosity and put back in the oxidation tubes. Oxidation tests are ordinarily continued either to the 100 milligram point or for 150 to 200 hours for so-called sludgeless oils.

The following example will illustrate the invention: 0.10 percent by weight of retene is added to an oil having an Indiana sludging Time of twenty-one hours and a viscosity rise of 9.50 seconds (Saybolt Universal) at 210 F. after fifty hours. Upon test the oil,with added retene, was found to have an Indiana sludging Time of thirty-four hours and a viscosity rise of 5.2 seconds (Saybolt Universal) at 210 F. after fifty hours.

The oil employed in the foregoing example was of Mid-Continent base and has the following characteristics:

Gravity; -1." A. P. I 24.8 Viscosity at 100 F Saybolt Universal 513 Viscosity at 210 F do 60.6 Viscosity index 79.2 Flash point F 435 Fire point F 500 Pour point F Acid number .025

Iodine number 20.2 Aniline point C 97.5

The proportion of retene to be incorporated in any given oil to obtain optimum results, will vary depending upon the oil itself. A propor-- tion of retene approximating that added to the oil in the foregoing example is generally ad-' vantageous.

While the invention is generally applicable to petroleum oils having a Saybolt Universal viscosity upwards of 50 seconds at 100 F., it is primarily concerned with petroleum oils, lubricating oils, for example, and heavy lubricating oils in particular, which are subjected to continuous use, as opposed to petroleum oils which are immediately consumed in use, and it is in this connection that the invention has its greatest utility. Where oil is to be consumed, burned for heating purposes in an oil heater, for example, the invention is not of equal importance as when the oil is being used over and over again, since ,utilization of an oil for burning involving destruction of the oil is inconsistent with its preservation for re-use. Again, for such purpose it is of less consequence that the oil have high resistance to sludge formation and changes with respect 'to viscosity since the oil is being subjccted to a use where these properties are of secondary importance. In either case, however, the addition of the oxidation inhibitor of the invention, in proper proportion, will inhibit sludge formation and retard changes with respect to viscosity, but its utility in one case is greater than in the other.

The terms oxidation inhibitor" and oxidation as used herein and in the claims are intended to be used in their broad rather than their narrow sense. Oxidation is intended to refer to the manner of formation of the undesirable substances in the oil, regardless of the precise manner of their formation. The inhibitor employed to retard or limit the formation of these undesirable substances has been termed an oxidation inhibitor" in the same sense.

I claim:

1. A petroleum lubricating oil having a Saybolt Universal viscosity upwards of 50 seconds at 100 F. containing about 0.1% by weight of retene.

2. A petroleum lubricating oil having a Say bolt Universal viscosity upwards of 50 seconds at F. containing upwards of about 0.05% 

